WO2009000553A1

WO2009000553A1 - Biogas plant

Info

Publication number: WO2009000553A1
Application number: PCT/EP2008/005298
Authority: WO
Inventors: Maximilian Hartmut Zerrer
Original assignee: Asw Anlagenbau, Schlamm- Und Wasertechnik Gmbh
Priority date: 2007-06-27
Filing date: 2008-06-27
Publication date: 2008-12-31

Abstract

The invention relates to a biogas plant which comprises a fermenter (2) into which a nutrient medium (M) can be introduced via an inlet opening (3') which medium is fermented to produce biogas (B). The invention is characterized in that a mixer (10) is mounted upstream of the fermenter (2), the nutrient medium (M) to be supplied to the fermenter (2) and a gaseous medium (G) being miscible in said mixer. The mixture of the nutrient medium (M) and the gaseous medium (G) thereby formed is supplied to the fermenter (2). Said mixture has a low specific weight due to the gas admixed, it therefore rises in the nutrient medium present in the fermenter and thoroughly mixes the nutrient medium.

Description

biogas plant

description

The invention relates to a biogas plant which has a fermenter into which a nutrient medium can be introduced via an inlet opening, through the fermentation of which biogas can be produced.

Such a biogas plant is known. For fermentation of the nutrient medium, it is necessary that the nutrient medium contained in the fermenter is mixed. Depending on the type of reactor used, the mixing of the nutrient medium is effected either by an agitator (stirred tank reactor) arranged in the reactor, or an air stream is introduced into a so-called airlift reactor, which ensures appropriate mixing of the nutrient medium in the reactor. In both cases, therefore, devices are required in the reactor, which provide either mechanical (agitator) or flow dynamics (airlift reactor) for a movement of the nutrient medium. Such device but expensive in a disadvantageous way the manufacturing, operating and maintenance costs of a known biogas plant.

EP 1 574 581 A2 discloses a method and an apparatus for producing methane gas, in which a starting material containing CO _{2 is} fed to a main reactor in which microorganisms are present which produce methane gas from CO ₂ and hydrogen. For this purpose, the starting material containing CO _{2 is} fed by means of a compressor to two reactors in which a pre-purification process takes place, in which a sorbent medium is present in the reactors, which selectively binds CO ₂ . When the sorbent medium is saturated with CO ₂ , the feed of the CO ₂ -containing starting material is stopped, so that a CO ₂ -rich starting medium is obtained, which is fed by means of another compressor to the main reactor. As a result, a continuous gas flow is supplied to this main reactor. Further, a hydrogen gas is supplied to the main reactor, and the microorganisms contained in the main reactor then generate methane from the CO ₂ and the hydrogen gas.

DE 43 33 177 describes a process for the treatment of biodegradable substrates, in which one or more streams are fed to a conditioning stage and mixed there by means of a stirrer. The conditioning stage is ventilated intermittently by means of a blower, whereby it can additionally be provided that the conditioning stage is heated via a hot water circuit. In the conditioning stage, an acidic environment and thermophilic temperatures of 40 ° to 55 ° are maintained to allow enzymatic hydrolysis of the biodegradable suspension. The bio-waste suspension homogenized and sanitized in the conditioning stage is then fed to the digestion stage, which is used as a conventional methane reactor with or without mobilized biomass is operated. It is provided that a portion of the digested substrate is returned via a return line in the conditioning stage, so that a metered inoculation of the conditioning is done with an anaerobic bacterial flora, the methanizing bacteria are selectively suppressed by the intermittent ventilation by means of the blower and only the oxygen-tolerant bacteria remain. The aeration and the homogenization in the conditioning stage are coordinated so that anaerobic and aerobic cycling of the microorganisms occurs both temporally and spatially. By this aerobic and anaerobic cycling of microorganisms in conjunction with the respective state in the conditioning stage adapted recirculation of digested substrate from the subsequent digestion via the return line as vaccine and balancing mass, it is possible to use a conventional buffer tank as a conditioning and this as a bioreactor use.

DE 42 30 644 C2 relates to a process for the conversion of carbon dioxide in the flue gas by bacterial fermentation to methane as the final stage of the flue gas cleaning in coal power plants. It is provided that flue gas is mixed under moderate pressure with water or dissolved in water, a fermentable substrate is prepared by enrichment with nutrients and growth substances and hydrogen and vaccination with methane-forming bacteria, this mixture is homogenized and then continuously in a reactor fermented to methane and the resulting methane is removed.

In all the aforementioned devices and methods is not provided that a thorough mixing of the fermenter to be supplied nutrient medium is performed.

It is an object of the present invention, a biogas plant of the type mentioned in such a way that in a simple manner a thorough mixing of the nutrient medium contained in the fermenter is achieved. This object is achieved in that the fermenter is preceded by a mixing device in which the fermenter to be supplied nutrient medium and a gaseous medium are mixable, that the thus formed mixture of nutrient medium and gaseous medium is fed to the fermenter, said mixture due to its by the gas admixture caused low specific gravity in the nutrient medium in the fermenter rises and mixes it.

The inventive method provides that before feeding the nutrient medium into the fermenter, the nutrient medium is mixed in a mixing device with a gaseous medium, and that the thus formed, by the gas admixture a low specific gravity having mixture of nutrient medium and gaseous medium in the Fermenter nutrient medium rises and thereby this is mixed.

The measures according to the invention advantageously provide a biogas plant which is suitable both for the mephophilic and the thermophilic area and in which no devices arranged inside the fermenter for mixing the nutrient medium are no longer required. The introduction of the thus mixed with the gaseous medium nutrient medium in the fermenter causes in an advantageous manner that a nutrient medium flow is formed in the fermenter, which causes a mixing of the nutrient medium therein. It is therefore no longer necessary to provide facilities such as a stirrer or air nozzles in the fermenter. This causes in an advantageous manner that in this way both the production costs of the fermenter and thus the biogas plant and their operating and maintenance costs are reduced.

An advantageous development of the invention provides that the gaseous medium used for mixing the nutrient medium obtained in the fermenter Biogas is. Such a measure has the advantage of a particularly cost-effective operation.

A further advantageous development of the invention provides that completely or partially fermented nutrient medium taken from the fermenter is passed to the mixing device, where it is mixed with the nutrient medium to be introduced into the fermenter and the gaseous medium and in turn fed into the fermenter. Such a procedure has the advantage that a circulation operation of the fermenter is thereby made possible.

A further advantageous development of the invention provides that the filling quantity of the nutrient medium in the fermenter can be regulated. Preferably, it is provided in this case that the filling quantity control takes place by regulating the supply and / or the removal of the nutrient medium as a function of the pressure of the biogas produced in the fermenter. This procedure has the advantage that in this way the pressure of the biogas in the fermenter can be kept below a defined pressure value in a simple manner.

A further advantageous development of the invention provides that the pressure is kept below the atmospheric pressure. This has the advantage that in this way the fermenter can be constructed particularly simple.

Further advantageous developments of the invention are the subject of the dependent claims.

Further details and advantages of the invention can be taken from the exemplary embodiment, which will be explained below with reference to the single figure. It shows:

Figure 1 is a schematic representation of a biogas plant FIG. 1 shows a biogas plant, generally designated 1, which has a fermenter 2 to which the nutrient medium M to be fermented in the fermenter 2 can be fed via a feed line 3. By fermenting the substrate-like culture medium biogas B is generated, which accumulates in a gas storage area 2a of the fermenter 2 and is discharged via a Gasabführleitung 4 from the fermenter 2 by valves 5a and 5b is opened or closed accordingly. The biogas B discharged from the fermenter 2 is either - as here - fed via a gas line 4a to a consumer 6 or fed into an external gas line system. Such a biogas plant 1 is known and therefore need not be explained further.

The biogas plant 1 described here is characterized in that the nutrient medium M to be supplied to the fermenter 2 is mixed with a gaseous medium G before it is fed. This has the advantage that the introduced into the fermenter 2 mixture of nutrient medium M and gaseous medium G ensures a mixing of the nutrient medium M located in the fermenter 2 by a from an inlet port 3 'of the feed line 3 outgoing nutrient medium flow S is generated, due to its caused by the gas admixture lower specific gravity in the nutrient medium M located in the fermenter 2 and thus ensures the same mixing. In the biogas plant 1 described, therefore, no devices such as, for example, an agitator, flow guide surfaces or air inlet nozzles for a separately introduced air flow are required in an advantageous manner. This advantageously reduces the production, operating and maintenance costs of the biogas plant 1 considerably.

The mixing of the nutrient medium M to be introduced into the fermenter 2 with the gaseous medium G is achieved in that the inlet opening 3 'for the nutrient medium M is preceded by a mixing device 10 which supplies both the nutrient medium M and the gaseous medium G. and then these two components in the mixing device 10th be mixed together. The mixture of nutrient medium M and gaseous medium G thus formed is then conducted via the feed line 3 from the mixing device 10 to the inlet opening 3 'of the fermenter 2.

For this purpose, it is provided that the mixing device 10 has a first input 10a, via which the nutrient medium M of the mixing device 10 can be fed. The substrate-like nutrient medium M in the case described here is primary sludge, which is supplied to the first input 10a of the mixing device 10 via a first feed pump 31. The primary sludge is optionally still excess sludge, which optionally also contains a co-fermented, fed via a second feed pump 32, wherein the supply of primary sludge and / or secondary sludge via valves 33 a, 33 b can be regulated. Shut-off valves 34a and 34b make it possible to control the supply of primary sludge to the first feed pump 31 or of excess sludge to the second coating pump 32.

The gaseous medium G is supplied to the mixing device 10 via a second input 10b. It is particularly advantageous if the gaseous medium G used for mixing the nutrient medium M does not originate - at least in part - from an external gas source, but rather that the biogas B obtained in the fermenter 2 is used for this purpose. For this purpose, it is provided in the exemplary embodiment described that the biogas B removed from the gas storage area 2 a of the fermenter 2 is supplied to the second input 10 b of the mixing device 10 by guiding a gas line 4 b provided with a valve 11 to the mixing device 10.

Preferably, it is provided that the gaseous medium G before being fed into the mixing device 10 is still compressed in a gas compressor 12 and fed via a gas pump 13 to the mixing device 10, so that the mixture formed in the mixing device 10 of nutrient medium M and gaseous medium G. a sufficiently high pressure in the fermenter 2 is fed. Such a measure has the advantage that in this way from the Inlet opening 3 'of the fermenter 2 exiting mixture of nutrient medium M and gaseous medium G, which - as already mentioned - by this mixture has a lower specific gravity than the other located in the fermenter 2 nutrient medium M, rises by this pressurization to an even better extent and thereby ensuring even better mixing of the nutrient medium M present in the fermenter 2.

The gas compressor can - if necessary - be used without addition of the nutrient medium M for feeding the gaseous medium G. As a result, the nutrient medium M, M 'present in the fermenter 2 can be homogenized.

Optionally, it can be provided that a control valve 14 is arranged between the gas compressor 12 and the gas pump 13.

The fermenter 2 further has a plurality of withdrawal points 7a, 7b for a completely or partially fermented nutrient medium M ', ie in the described embodiment for a sludge obtained from a fed sewage sludge, so that the fermented nutrient medium M' then via one or more discharge lines 8a 8b can be removed from the fermenter 2 by opening corresponding valves 9a, 9b. The fermented medium M 'is then removed via a withdrawal line 8c of the biogas plant 1 by actuating a valve 9c which opens and closes the withdrawal line 8c.

In the case described here it is provided that the mixing device 10 is not only the nutrient medium M - here: the sewage sludge - and the gaseous medium G - here: obtained by the fermentation of the nutrient medium M biogas B - is fed, but that in an advantageous manner is provided and that the mixing device 10 is also supplied from the fermenter 2 via a line 8d, fermented nutrient medium M 'is supplied via a third input 10c, mixed with the nutrient medium M and the gaseous medium G and then from the nutrient medium M. and / or the returned, completely or partially fermented nutrient medium M 'and the gaseous medium G composite mixture is in turn fed into the fermenter 2. Such an approach has the advantage that this allows a circulation operation of the fermenter 2, by which an improved mixing in the fermenter 2 nutrient medium M, M 'can be achieved. The procedure described makes it possible to dispense with a required in known systems, additional delivery unit.

In order to supply the fermenter 2 with the process heat required for a rapid fermentation of the nutrient medium M supplied, it is provided in the described embodiment that the biogas B removed from the fermenter 2 - as already described - a consumer 6 designed here as a gas engine 6 'for recovery the heat required for the fermentation process is supplied. The gas engine 6 'is connected via a feed line 6a and a discharge line 6b to a heat exchanger 16, which transfers the heat generated by the gas engine 6' and transferred via the lines 6a, 6b to the heat exchanger 16 to the returned nutrient medium M 'and thus for an energy input into the fermenter 2 provides. But it is also possible, instead of the recirculated nutrient medium M 'the biogas plant 1 supplied nutrient medium M, ie the primary sludge to heat in the aforementioned manner. It is also possible to dispense with the above-described manner of obtaining the process heat to accelerate the fermentation of the nutrient medium M and the fermenter 2 by means of an external source - for example, electrically, geothermally, by burning fossil fuels or vegetable or thermal residues , etc. - to heat.

It is preferably provided that - as schematically indicated in FIG. 1 - the feed line 3 connecting the mixing device 10 to the fermenter 2 is arranged in a manhole already present for the purpose of cleaning the empty fermenter 2, thereby providing a simple and inexpensive way of loading fermenter 2 is possible without expensive ments through the wall of the fermenter s 2 and / or additional connections are required.

The accumulation of the biogas B obtained by the fermentation of the nutrient medium M in the gas storage area 2 a of the fermenter 2 causes an overpressure to be built up as a result. This had the consequence that the hitherto used fermenter 2 and thus the biogas plant 1 had to be designed sufficiently pressure-resistant to meet the legal requirements, for example, the German pressure vessel regulation. In addition, the known fermenter 2 usually approved by the authorities and regularly checked by experts. The described biogas plant 1 now makes it possible to keep the pressure in the fermenter 2 below a certain pressure level, for example below the atmospheric pressure, by providing that by a corresponding regulation of the filling amount F by changing the supply of the nutrient medium M and / or the removal of the nutrient medium M 'of the pressure prevailing in the fermenter 2 total pressure is kept below a bar. For this purpose, the pressure of the biogas B produced in the fermenter 2 is detected continuously, quasi-continuously or at certain discrete points in time by means of a gas pressure sensor 20 and the sensor signal generated by the gas pressure sensor 20 is fed to a control device 30. For the sake of clarity, the signal lines running to and from the control device 30 are not shown in FIG.

If the pressure of biogas B in line 4 and thus in fermenter 2 is too high, the supply of nutrient medium M is reduced and / or the nutrient medium M 'is increasingly removed from fermenter 2 via lines 8a, 8b, 8c. As a result, the volume of the nutrient medium M ₁ M 'located in the fermenter 2 is reduced, thereby increasing the gas storage area 2 a available to the biogas B produced, which results in a lowering of the gas pressure in the fermenter 2. If the gas pressure in the fermenter 2 is too low, for example as a result of excessively high removal of biogas B, nutrient medium M is supplied to fermenter 2 in an increased degree and nutrient medium M 'is removed from fermenter 2 to a lesser extent, so that gas G is removed Available gas storage area 2a of the fermenter 2 is reduced and thereby the gas pressure is increased. It is also possible to feed the fermenter 2 already fermented nutrient medium M ', which was discharged via the line 8c, again via a line 8e in order to increase the short-term possible removal of gas without loss of pressure.

In summary, it should be noted that by the described procedure an improved mixing of the nutrient medium M, M 'in the fermenter 2 in a simple manner can be achieved, which optionally can be provided that by an appropriate control of the supply and / or the removal of nutrient medium M or M 'of the pressure prevailing in the fermenter 2 gas pressure below a certain value, preferably below the atmospheric pressure, can be maintained. The plant described is therefore characterized by low manufacturing, operating and maintenance costs and requires - if the latter alternative is realized - no regulatory approval.

Claims

claims

1. biogas plant, which has a fermenter (2) into which via an inlet port (3 ') a nutrient medium (M) can be introduced through the fermentation of biogas (B) can be generated, characterized in that the fermenter (2) has a mixing device (10) upstream, in which the fermenter (2) to be supplied nutrient medium (M) and a gaseous medium (G) are mixable, and that the thus formed mixture of nutrient medium (M) and gaseous medium (G) the fermenter (2 ), wherein this mixture rises due to its caused by the gas admixture low specific gravity in the nutrient medium contained in the fermenter and mixes it.

2. Biogas plant according to claim 1, characterized in that the mixing device (10) has a first input (10 a), via which the mixing device (10), the nutrient medium (M) is supplied.

3. Biogas plant according to claim 1, characterized in that the mixing device (10) has a second input (10b), via which the mixing device (10), the gaseous medium (G) is supplied.

4. Biogas plant according to one of the preceding claims, characterized in that the biogas plant (1) has a gas line (12) through which from a gas storage area (2a) of the fermenter (2) biogas removed (B) the second input (10b) of the Mixing device (10) can be fed.

5. biogas plant according to claim 3, characterized in that the second input (10c), the mixing device (10) is preceded by a gas compressor (12) and / or a gas pump (13).

6. Biogas plant according to one of the preceding claims, characterized in that the mixing device (10) has a third input (10c) via which a fermenter (2) taken nutrient medium (M ') of the mixing device (10) can be fed.

7. biogas plant according to one of the preceding claims, characterized in that the fermenter (2) one or more sampling points (7a, 7b) for the in the fermenter (2) located, wholly or partially fermented nutrient medium (M ').

8. Biogas plant according to one of the preceding claims, characterized in that the biogas plant (1) has a heat exchanger (16) through which the nutrient medium (M; M ') the process heat required for fermentation can be supplied.

9. biogas plant according to one of the preceding claims, characterized in that the biogas plant (1) has a control device (30) through which the filling quantity (F) of the in the fermenter (2) located nutrient medium (M, M ') is adjustable.

10. Biogas plant according to one of the preceding claims, characterized in that the regulation of the filling quantity (F) by regulating the supply and / or removal of the nutrient medium (M, M ') in dependence on the pressure of the biogas produced in the fermenter (2) ( B).

11.Verfahren for fermentation of a nutrient medium (M) in a fermenter (2) of a biogas plant (1), characterized in that before the feeding of the nutrient medium (M) in the fermenter (2) the nutrient medium in a mixing device (10) with a gaseous medium (G) is mixed and the thus formed material / gas mixture is introduced into the fermenter (2), and that thus formed by the gas admixing a low specific weight having mixture of nutrient medium and gaseous medium (2) in the nutrient medium (M) located in the fermenter and thus this is mixed.

12. The method according to claim 11, characterized in that the gaseous medium (G) of the mixing device (10) is supplied under pressure.

13. The method according to any one of the preceding claims, characterized in that the gaseous medium (G) in the fermenter (2) biogas produced (B) is used.

14. The method according to any one of claims 11 to 13, characterized in that the mixing device (10) from the fermenter (2) taken nutrient medium (M ') is supplied.